THE BACILLUS FOR SMALL ANLMALS 169 



that the toxicity of Johne's bacillus is not great, 

 and that a diseased animal is but little affected until 

 the large masses of bacilli, and the pressing of new- 

 tissue on the glands, lead to derangement of food 

 absorption, malnutrition, and diarrhoea ; all the obser- 

 vations and experiments of the authors tend to confirm 

 this view. In an intestinal disease the number of 

 factors influencing the general health must be con- 

 siderable, and, as we have already seen, an exactly 

 opposite condition of affairs may exist — />., the pre- 

 sence of a large number of bacilli with a comparatively 

 robust state of health of the animal. 



We have alread}^ seen that certain investigators 

 reproduced the disease in calves, but the doses of 

 infected material used were often very large, and some- 

 times repeated. The experiments of the authors with 

 pure cultures of the bacillus gave the same results. 

 To reproduce the disease in a susceptible animal, it 

 was necessary to inoculate much larger doses of 

 Johne's bacillus than would have been necessary to 

 produce tuberculosis with the tubercle bacillus. 



But, even when the typical disease is present, it 

 must be remembered that the bacilli and lesions are 

 confined to the intestine and glands, and the question 

 arises as to whether there are not, in the case of 

 Johne's bacillus, special factors, besides the production 

 of toxins by the bacillus and the active resistance of 

 the host, which help to determine its pathogenicity, 

 and in the case of susceptible animals, its distribution. 

 It may be that in the body, as in artificial culture media, 

 special foodstuffs are necessary for its vitality, and 

 that these exist in sufficient quantity only in the walls 

 of the intestine and in the mesenteric glands of certain 

 ruminants. It is to be presumed that such foodstuffs 

 cannot exist in large quantities, even in the intestine, 



